The present invention relates generally to the field of vehicle safety systems. Specifically, the present invention relates to a driver airbag device mounted in a steering wheel of an automobile and a folded airbag included in the airbag device.
Japanese Unexamined Patent Application Publication No. 10-44900 (incorporated by reference herein) discloses a method of folding a driver airbag into a substantially rectangular parallelepiped folded body. the method includes the steps of spreading the airbag, which is circular in an unfolded state; folding a left end portion and a right end portion of the airbag inward so as to obtain a band-shaped folded body that extends in a vertical direction (which is herein defined as a vertical direction in a state in which the airbag is mounted in the steering wheel); and then folding an upper portion and a lower portion of the band-shaped folded body along horizontal folding lines (see FIG. 1 in the above-mentioned publication).
The above-mentioned publication also describes a known method of obtaining a substantially rectangular parallelepiped folded airbag as an example of the related art (see FIG. 4 in the above-mentioned publication). This method includes the steps of folding an upper portion and a lower portion of a circular airbag along horizontal folding lines so as to obtain a band-shaped folded body that extends in the horizontal direction, and then folding a left portion and a right portion of the band-shaped folded body along vertical folding lines.
The folded airbag according to Japanese Unexamined Patent Application Publication No. 10-44900 substantially evenly inflates in the horizontal direction until it reaches a fully deployed shape.